For the construction or retesting of pipe, whether it is pipelines, process piping within a facility or pressure vessels, the procedure to confirm the integrity of such equipment, as required by regulations, is to apply an internal pressure 1.1 to 1.5 times greater than the maximum allowable operating pressure or maximum operating pressure. The test is used to confirm the quality of the welds and ensure the main body of the pressure equipment can handle the stresses of normal operating conditions and the occasional upset conditions where excessive pressure occurs. The pressure tests is performed using a liquid medium such as water and in some cases a combination of water and an anti-freezing agent (i.e., methanol); this test is called a hydrotest. The alternative to a hydrotest is a pneumatic test that utilizes a gas such as air or nitrogen to provide pressure. The procedure of pressure testing pipe and pipelines is theoretically straightforward but can be very difficult logistically.
When using water to apply pressure, the sheer volume may be difficult and costly to acquire. When it is necessary to add an anti-freezing agent the cost will increase significantly. To complicate it further, it is encouraged to use “fresh” water to prevent contamination, corrosion and the introduction of bacteria. It is beneficial to use “fresh” water, however it is not readily available as is water produced with oil and gas, which is generally abundant at production facilities or near where the pipeline is buried. Fresh water has to be trucked to site to perform a pressure test.
A pneumatic test presents different challenges. Air is readily available but its use is discouraged for it has corrosive properties with even a small concentration of water. Nitrogen, an alternative to air, is an inert gas, meaning non-reactive or non-corrosive, however, it will come at a greater cost when large volumes are required. The greatest concern employing a pneumatic test is the compressibility and “stored energy” of the gas. The results from a rupture can be catastrophic. The sudden release of pressure can launch projectiles several meters if not hundreds of meters and potentially cause fatalities.
While the devices heretofore fulfill their respective, particular objectives and requirements, they do not provide an apparatus for testing long lengths of piping or pipe sections that have bends as such there exists a need for a new apparatus, which substantially departs from the prior art, and in doing so provides an apparatus primarily developed for the purpose of pressure testing piping with reduced testing fluid volume.